1. The Tensile Test Results for ASTM A335 P92 Pipe Bends

The mechanical properties of the four pieces of ASTM A335 P92 pipe bends shall be tested and reviewed. It includes tensile strength, yield strength, elongation, as well as the impact test value. Tensile tests were conducted at room temperature and elevated temperature on both longitudinal(“L”) and transverse directions(“T”). The specimens were taken respectively from the ASTM A335 P92 raw pipe, bend-starting area, bend-ending area, outer-back-arc area of the finished pipe bends. In below 4 tables, “Y.S” stands for yield strength with the unit “MPa”, “T.S” stands for tensile strength with the unit “MPa”, “EL.” stands for elongation with the unit “%”, “A_kv” stands for the average energy absorption in impact test with an unit of “J”. Besides, “RM”: raw material, “BS”: bend-starting area, “BE”: bend-ending area, “BA”: bending-back-arc area, “R.T”: room temperature, “E.T”: elevated temperature.

Tensile Test		RM		BS		BE		BA
Direction		L	T	L	T	L	T	L	T
R.T	Y.S	565	575	565	575	590	590	580	575
	T.S	705	720	715	720	735	730	725	735
	EL.	23	21	20	22	24	27	22	23
	Akv	87	95	87	95	139	97	125	86
E.T	Y.S	308	339	319	322	332	332	335	328
	T.S	341	359	340	340	349	349	336	345
	EL.	28	30	32	32	38	38	30	29

*The tensile test results for item B1 of P92 pipe bend.

Tensile Test		RM		BS		BE		BA
Direction		L	T	L	T	L	T	L	T
R.T	Y.S	565	575	620	625	655	655	625	630
	T.S	705	720	745	755	775	780	755	760
	EL.	23	21	25	23	20	22	27	22
	Akv	87	95	138	84	56	65	94	55
E.T	Y.S	308	339	339	351	337	384	351	347
	T.S	341	359	359	371	360	390	366	364
	EL.	28	30	28	34	33	34	26	30

*The tensile test results for item B2 of P92 pipe bend.

Tensile Test		RM		BS		BE		BA
Direction		L	T	L	T	L	T	L	T
R.T	Y.S	555	560	540	545	565	570	560	565
	T.S	705	710	685	690	705	715	705	705
	EL.	23.5	22.5	23	24	22	21	22.5	22
	Akv	130	90	134	93	60	51	73	61
E.T	Y.S	300	310	310	310	325	320	325	325
	T.S	345	360	355	360	370	365	370	365
	EL.	23.5	22.5	30.5	30.5	30	30	29	25

*The tensile test results for item B3 of P92 pipe bend.

Tensile Test		RM		BS		BE		BA
Direction		L	T	L	T	L	T	L	T
R.T	Y.S	490	495	535	530	540	550	565	540
	T.S	660	665	695	690	700	705	715	700
	EL.	26.5	24.5	23.5	23.5	24.5	24.5	23	22
	Akv	115	88	118	78	74	49	107	50
E.T	Y.S	300	305	320	310	325	340	340	335
	T.S	325	325	335	330	340	355	360	365
	EL.	28	31	30	26	30.5	27	26	25

*The tensile test results for item B4 of P92 pipe bends.

Analysis & Conclusion: Optimum Working Conditions for P92/ T92 Bending

Based on the data above-listed and that provided by “A335 P92 bending process overview” in last article,

1. All the finished ASTM A335 P92 pipe bends conform to chemical composition requirements, mechanical properties requirements at both room & elevated temperatures.
2. Corresponding to its lower yield & tensile strength, the raw-pipe hardness of item B4 is also lower than the other 3 pieces of raw pipe. This verifies that in non-destructive test hardness is an important parameter to evaluate the strength.
3. The wall thickness deduction rate after bending is generally okay for all 4 pipes which is negatively correlated to the ratio of bend-centerline-radius to outside diameter of the pipe. The hardness values of finished products in different areas conform to the standard. The microstructure of P92 raw material and finished products are in conformance. No intergranular cracking exists.
4. Among the 4 different portfolios of working-temperature and bending rate(velocity), item B4 has the most uniform strength distribution in different area of finished pipe bends.
5. Due to the relatively faster bending velocity, the yield strength at room temperature increased while its yield ration decreased. It means faster bending velocity may result in negative effect on the P92/ T92 steel.
6. For the manufacture of ASTM A335 P92 or ASTM A213 T92 pipe bends, the optimum working temperature should be 920°C±10°C while the best bending rate(velocity) shall be 10~15 mm per minute.